Merge patch series "riscv: Add remaining module relocations and tests"

Charlie Jenkins <charlie@rivosinc.com> says:

A handful of module relocations were missing, this patch includes the
remaining ones. I also wrote some test cases to ensure that module
loading works properly. Some relocations cannot be supported in the
kernel, these include the ones that rely on thread local storage and
dynamic linking.

This patch also overhauls the implementation of ADD/SUB/SET/ULEB128
relocations to handle overflow. "Overflow" is different for ULEB128
since it is a variable-length encoding that the compiler can be expected
to generate enough space for. Instead of overflowing, ULEB128 will
expand into the next 8-bit segment of the location.

A psABI proposal [1] was merged that mandates that SET_ULEB128 and
SUB_ULEB128 are paired, however the discussion following the merging of
the pull request revealed that while the pull request was valid, it
would be better for linkers to properly handle this overflow. This patch
proactively implements this methodology for future compatibility.

This can be tested by enabling KUNIT, RUNTIME_KERNEL_TESTING_MENU, and
RISCV_MODULE_LINKING_KUNIT.

[1] https://github.com/riscv-non-isa/riscv-elf-psabi-doc/pull/403

* b4-shazam-merge:
  riscv: Add tests for riscv module loading
  riscv: Add remaining module relocations
  riscv: Avoid unaligned access when relocating modules

Link: https://lore.kernel.org/r/20231101-module_relocations-v9-0-8dfa3483c400@rivosinc.com
Signed-off-by: Palmer Dabbelt <palmer@rivosinc.com>

1 files changed, 499 insertions, 104 deletions

diff --git a/arch/riscv/kernel/module.c b/arch/riscv/kernel/module.c
index 7c651d55fcbd..4b339729d5ec 100644
--- a/arch/riscv/kernel/module.c
+++ b/arch/riscv/kernel/module.c
@@ -7,6 +7,9 @@
 #include <linux/elf.h>
 #include <linux/err.h>
 #include <linux/errno.h>
+#include <linux/hashtable.h>
+#include <linux/kernel.h>
+#include <linux/log2.h>
 #include <linux/moduleloader.h>
 #include <linux/vmalloc.h>
 #include <linux/sizes.h>
@@ -14,6 +17,38 @@
 #include <asm/alternative.h>
 #include <asm/sections.h>
 
+struct used_bucket {
+	struct list_head head;
+	struct hlist_head *bucket;
+};
+
+struct relocation_head {
+	struct hlist_node node;
+	struct list_head *rel_entry;
+	void *location;
+};
+
+struct relocation_entry {
+	struct list_head head;
+	Elf_Addr value;
+	unsigned int type;
+};
+
+struct relocation_handlers {
+	int (*reloc_handler)(struct module *me, void *location, Elf_Addr v);
+	int (*accumulate_handler)(struct module *me, void *location,
+				  long buffer);
+};
+
+unsigned int initialize_relocation_hashtable(unsigned int num_relocations);
+void process_accumulated_relocations(struct module *me);
+int add_relocation_to_accumulate(struct module *me, int type, void *location,
+				 unsigned int hashtable_bits, Elf_Addr v);
+
+struct hlist_head *relocation_hashtable;
+
+struct list_head used_buckets_list;
+
 /*
  * The auipc+jalr instruction pair can reach any PC-relative offset
  * in the range [-2^31 - 2^11, 2^31 - 2^11)
@@ -27,68 +62,90 @@ static bool riscv_insn_valid_32bit_offset(ptrdiff_t val)
 #endif
 }
 
-static int apply_r_riscv_32_rela(struct module *me, u32 *location, Elf_Addr v)
+static int riscv_insn_rmw(void *location, u32 keep, u32 set)
+{
+	u16 *parcel = location;
+	u32 insn = (u32)le16_to_cpu(parcel[0]) | (u32)le16_to_cpu(parcel[1]) << 16;
+
+	insn &= keep;
+	insn |= set;
+
+	parcel[0] = cpu_to_le16(insn);
+	parcel[1] = cpu_to_le16(insn >> 16);
+	return 0;
+}
+
+static int riscv_insn_rvc_rmw(void *location, u16 keep, u16 set)
+{
+	u16 *parcel = location;
+	u16 insn = le16_to_cpu(*parcel);
+
+	insn &= keep;
+	insn |= set;
+
+	*parcel = cpu_to_le16(insn);
+	return 0;
+}
+
+static int apply_r_riscv_32_rela(struct module *me, void *location, Elf_Addr v)
 {
 	if (v != (u32)v) {
 		pr_err("%s: value %016llx out of range for 32-bit field\n",
 		       me->name, (long long)v);
 		return -EINVAL;
 	}
-	*location = v;
+	*(u32 *)location = v;
 	return 0;
 }
 
-static int apply_r_riscv_64_rela(struct module *me, u32 *location, Elf_Addr v)
+static int apply_r_riscv_64_rela(struct module *me, void *location, Elf_Addr v)
 {
 	*(u64 *)location = v;
 	return 0;
 }
 
-static int apply_r_riscv_branch_rela(struct module *me, u32 *location,
+static int apply_r_riscv_branch_rela(struct module *me, void *location,
 				     Elf_Addr v)
 {
-	ptrdiff_t offset = (void *)v - (void *)location;
+	ptrdiff_t offset = (void *)v - location;
 	u32 imm12 = (offset & 0x1000) << (31 - 12);
 	u32 imm11 = (offset & 0x800) >> (11 - 7);
 	u32 imm10_5 = (offset & 0x7e0) << (30 - 10);
 	u32 imm4_1 = (offset & 0x1e) << (11 - 4);
 
-	*location = (*location & 0x1fff07f) | imm12 | imm11 | imm10_5 | imm4_1;
-	return 0;
+	return riscv_insn_rmw(location, 0x1fff07f, imm12 | imm11 | imm10_5 | imm4_1);
 }
 
-static int apply_r_riscv_jal_rela(struct module *me, u32 *location,
+static int apply_r_riscv_jal_rela(struct module *me, void *location,
 				  Elf_Addr v)
 {
-	ptrdiff_t offset = (void *)v - (void *)location;
+	ptrdiff_t offset = (void *)v - location;
 	u32 imm20 = (offset & 0x100000) << (31 - 20);
 	u32 imm19_12 = (offset & 0xff000);
 	u32 imm11 = (offset & 0x800) << (20 - 11);
 	u32 imm10_1 = (offset & 0x7fe) << (30 - 10);
 
-	*location = (*location & 0xfff) | imm20 | imm19_12 | imm11 | imm10_1;
-	return 0;
+	return riscv_insn_rmw(location, 0xfff, imm20 | imm19_12 | imm11 | imm10_1);
 }
 
-static int apply_r_riscv_rvc_branch_rela(struct module *me, u32 *location,
+static int apply_r_riscv_rvc_branch_rela(struct module *me, void *location,
 					 Elf_Addr v)
 {
-	ptrdiff_t offset = (void *)v - (void *)location;
+	ptrdiff_t offset = (void *)v - location;
 	u16 imm8 = (offset & 0x100) << (12 - 8);
 	u16 imm7_6 = (offset & 0xc0) >> (6 - 5);
 	u16 imm5 = (offset & 0x20) >> (5 - 2);
 	u16 imm4_3 = (offset & 0x18) << (12 - 5);
 	u16 imm2_1 = (offset & 0x6) << (12 - 10);
 
-	*(u16 *)location = (*(u16 *)location & 0xe383) |
-		    imm8 | imm7_6 | imm5 | imm4_3 | imm2_1;
-	return 0;
+	return riscv_insn_rvc_rmw(location, 0xe383,
+			imm8 | imm7_6 | imm5 | imm4_3 | imm2_1);
 }
 
-static int apply_r_riscv_rvc_jump_rela(struct module *me, u32 *location,
+static int apply_r_riscv_rvc_jump_rela(struct module *me, void *location,
 				       Elf_Addr v)
 {
-	ptrdiff_t offset = (void *)v - (void *)location;
+	ptrdiff_t offset = (void *)v - location;
 	u16 imm11 = (offset & 0x800) << (12 - 11);
 	u16 imm10 = (offset & 0x400) >> (10 - 8);
 	u16 imm9_8 = (offset & 0x300) << (12 - 11);
@@ -98,16 +155,14 @@ static int apply_r_riscv_rvc_jump_rela(struct module *me, u32 *location,
 	u16 imm4 = (offset & 0x10) << (12 - 5);
 	u16 imm3_1 = (offset & 0xe) << (12 - 10);
 
-	*(u16 *)location = (*(u16 *)location & 0xe003) |
-		    imm11 | imm10 | imm9_8 | imm7 | imm6 | imm5 | imm4 | imm3_1;
-	return 0;
+	return riscv_insn_rvc_rmw(location, 0xe003,
+			imm11 | imm10 | imm9_8 | imm7 | imm6 | imm5 | imm4 | imm3_1);
 }
 
-static int apply_r_riscv_pcrel_hi20_rela(struct module *me, u32 *location,
+static int apply_r_riscv_pcrel_hi20_rela(struct module *me, void *location,
 					 Elf_Addr v)
 {
-	ptrdiff_t offset = (void *)v - (void *)location;
-	s32 hi20;
+	ptrdiff_t offset = (void *)v - location;
 
 	if (!riscv_insn_valid_32bit_offset(offset)) {
 		pr_err(
@@ -116,23 +171,20 @@ static int apply_r_riscv_pcrel_hi20_rela(struct module *me, u32 *location,
 		return -EINVAL;
 	}
 
-	hi20 = (offset + 0x800) & 0xfffff000;
-	*location = (*location & 0xfff) | hi20;
-	return 0;
+	return riscv_insn_rmw(location, 0xfff, (offset + 0x800) & 0xfffff000);
 }
 
-static int apply_r_riscv_pcrel_lo12_i_rela(struct module *me, u32 *location,
+static int apply_r_riscv_pcrel_lo12_i_rela(struct module *me, void *location,
 					   Elf_Addr v)
 {
 	/*
 	 * v is the lo12 value to fill. It is calculated before calling this
 	 * handler.
 	 */
-	*location = (*location & 0xfffff) | ((v & 0xfff) << 20);
-	return 0;
+	return riscv_insn_rmw(location, 0xfffff, (v & 0xfff) << 20);
 }
 
-static int apply_r_riscv_pcrel_lo12_s_rela(struct module *me, u32 *location,
+static int apply_r_riscv_pcrel_lo12_s_rela(struct module *me, void *location,
 					   Elf_Addr v)
 {
 	/*
@@ -142,15 +194,12 @@ static int apply_r_riscv_pcrel_lo12_s_rela(struct module *me, u32 *location,
 	u32 imm11_5 = (v & 0xfe0) << (31 - 11);
 	u32 imm4_0 = (v & 0x1f) << (11 - 4);
 
-	*location = (*location & 0x1fff07f) | imm11_5 | imm4_0;
-	return 0;
+	return riscv_insn_rmw(location, 0x1fff07f, imm11_5 | imm4_0);
 }
 
-static int apply_r_riscv_hi20_rela(struct module *me, u32 *location,
+static int apply_r_riscv_hi20_rela(struct module *me, void *location,
 				   Elf_Addr v)
 {
-	s32 hi20;
-
 	if (IS_ENABLED(CONFIG_CMODEL_MEDLOW)) {
 		pr_err(
 		  "%s: target %016llx can not be addressed by the 32-bit offset from PC = %p\n",
@@ -158,22 +207,20 @@ static int apply_r_riscv_hi20_rela(struct module *me, u32 *location,
 		return -EINVAL;
 	}
 
-	hi20 = ((s32)v + 0x800) & 0xfffff000;
-	*location = (*location & 0xfff) | hi20;
-	return 0;
+	return riscv_insn_rmw(location, 0xfff, ((s32)v + 0x800) & 0xfffff000);
 }
 
-static int apply_r_riscv_lo12_i_rela(struct module *me, u32 *location,
+static int apply_r_riscv_lo12_i_rela(struct module *me, void *location,
 				     Elf_Addr v)
 {
 	/* Skip medlow checking because of filtering by HI20 already */
 	s32 hi20 = ((s32)v + 0x800) & 0xfffff000;
 	s32 lo12 = ((s32)v - hi20);
-	*location = (*location & 0xfffff) | ((lo12 & 0xfff) << 20);
-	return 0;
+
+	return riscv_insn_rmw(location, 0xfffff, (lo12 & 0xfff) << 20);
 }
 
-static int apply_r_riscv_lo12_s_rela(struct module *me, u32 *location,
+static int apply_r_riscv_lo12_s_rela(struct module *me, void *location,
 				     Elf_Addr v)
 {
 	/* Skip medlow checking because of filtering by HI20 already */
@@ -181,20 +228,18 @@ static int apply_r_riscv_lo12_s_rela(struct module *me, u32 *location,
 	s32 lo12 = ((s32)v - hi20);
 	u32 imm11_5 = (lo12 & 0xfe0) << (31 - 11);
 	u32 imm4_0 = (lo12 & 0x1f) << (11 - 4);
-	*location = (*location & 0x1fff07f) | imm11_5 | imm4_0;
-	return 0;
+
+	return riscv_insn_rmw(location, 0x1fff07f, imm11_5 | imm4_0);
 }
 
-static int apply_r_riscv_got_hi20_rela(struct module *me, u32 *location,
+static int apply_r_riscv_got_hi20_rela(struct module *me, void *location,
 				       Elf_Addr v)
 {
-	ptrdiff_t offset = (void *)v - (void *)location;
-	s32 hi20;
+	ptrdiff_t offset = (void *)v - location;
 
 	/* Always emit the got entry */
 	if (IS_ENABLED(CONFIG_MODULE_SECTIONS)) {
-		offset = module_emit_got_entry(me, v);
-		offset = (void *)offset - (void *)location;
+		offset = (void *)module_emit_got_entry(me, v) - location;
 	} else {
 		pr_err(
 		  "%s: can not generate the GOT entry for symbol = %016llx from PC = %p\n",
@@ -202,22 +247,19 @@ static int apply_r_riscv_got_hi20_rela(struct module *me, u32 *location,
 		return -EINVAL;
 	}
 
-	hi20 = (offset + 0x800) & 0xfffff000;
-	*location = (*location & 0xfff) | hi20;
-	return 0;
+	return riscv_insn_rmw(location, 0xfff, (offset + 0x800) & 0xfffff000);
 }
 
-static int apply_r_riscv_call_plt_rela(struct module *me, u32 *location,
+static int apply_r_riscv_call_plt_rela(struct module *me, void *location,
 				       Elf_Addr v)
 {
-	ptrdiff_t offset = (void *)v - (void *)location;
+	ptrdiff_t offset = (void *)v - location;
 	u32 hi20, lo12;
 
 	if (!riscv_insn_valid_32bit_offset(offset)) {
 		/* Only emit the plt entry if offset over 32-bit range */
 		if (IS_ENABLED(CONFIG_MODULE_SECTIONS)) {
-			offset = module_emit_plt_entry(me, v);
-			offset = (void *)offset - (void *)location;
+			offset = (void *)module_emit_plt_entry(me, v) - location;
 		} else {
 			pr_err(
 			  "%s: target %016llx can not be addressed by the 32-bit offset from PC = %p\n",
@@ -228,15 +270,14 @@ static int apply_r_riscv_call_plt_rela(struct module *me, u32 *location,
 
 	hi20 = (offset + 0x800) & 0xfffff000;
 	lo12 = (offset - hi20) & 0xfff;
-	*location = (*location & 0xfff) | hi20;
-	*(location + 1) = (*(location + 1) & 0xfffff) | (lo12 << 20);
-	return 0;
+	riscv_insn_rmw(location, 0xfff, hi20);
+	return riscv_insn_rmw(location + 4, 0xfffff, lo12 << 20);
 }
 
-static int apply_r_riscv_call_rela(struct module *me, u32 *location,
+static int apply_r_riscv_call_rela(struct module *me, void *location,
 				   Elf_Addr v)
 {
-	ptrdiff_t offset = (void *)v - (void *)location;
+	ptrdiff_t offset = (void *)v - location;
 	u32 hi20, lo12;
 
 	if (!riscv_insn_valid_32bit_offset(offset)) {
@@ -248,18 +289,17 @@ static int apply_r_riscv_call_rela(struct module *me, u32 *location,
 
 	hi20 = (offset + 0x800) & 0xfffff000;
 	lo12 = (offset - hi20) & 0xfff;
-	*location = (*location & 0xfff) | hi20;
-	*(location + 1) = (*(location + 1) & 0xfffff) | (lo12 << 20);
-	return 0;
+	riscv_insn_rmw(location, 0xfff, hi20);
+	return riscv_insn_rmw(location + 4, 0xfffff, lo12 << 20);
 }
 
-static int apply_r_riscv_relax_rela(struct module *me, u32 *location,
+static int apply_r_riscv_relax_rela(struct module *me, void *location,
 				    Elf_Addr v)
 {
 	return 0;
 }
 
-static int apply_r_riscv_align_rela(struct module *me, u32 *location,
+static int apply_r_riscv_align_rela(struct module *me, void *location,
 				    Elf_Addr v)
 {
 	pr_err(
@@ -268,91 +308,441 @@ static int apply_r_riscv_align_rela(struct module *me, u32 *location,
 	return -EINVAL;
 }
 
-static int apply_r_riscv_add16_rela(struct module *me, u32 *location,
+static int apply_r_riscv_add8_rela(struct module *me, void *location, Elf_Addr v)
+{
+	*(u8 *)location += (u8)v;
+	return 0;
+}
+
+static int apply_r_riscv_add16_rela(struct module *me, void *location,
 				    Elf_Addr v)
 {
 	*(u16 *)location += (u16)v;
 	return 0;
 }
 
-static int apply_r_riscv_add32_rela(struct module *me, u32 *location,
+static int apply_r_riscv_add32_rela(struct module *me, void *location,
 				    Elf_Addr v)
 {
 	*(u32 *)location += (u32)v;
 	return 0;
 }
 
-static int apply_r_riscv_add64_rela(struct module *me, u32 *location,
+static int apply_r_riscv_add64_rela(struct module *me, void *location,
 				    Elf_Addr v)
 {
 	*(u64 *)location += (u64)v;
 	return 0;
 }
 
-static int apply_r_riscv_sub16_rela(struct module *me, u32 *location,
+static int apply_r_riscv_sub8_rela(struct module *me, void *location, Elf_Addr v)
+{
+	*(u8 *)location -= (u8)v;
+	return 0;
+}
+
+static int apply_r_riscv_sub16_rela(struct module *me, void *location,
 				    Elf_Addr v)
 {
 	*(u16 *)location -= (u16)v;
 	return 0;
 }
 
-static int apply_r_riscv_sub32_rela(struct module *me, u32 *location,
+static int apply_r_riscv_sub32_rela(struct module *me, void *location,
 				    Elf_Addr v)
 {
 	*(u32 *)location -= (u32)v;
 	return 0;
 }
 
-static int apply_r_riscv_sub64_rela(struct module *me, u32 *location,
+static int apply_r_riscv_sub64_rela(struct module *me, void *location,
 				    Elf_Addr v)
 {
 	*(u64 *)location -= (u64)v;
 	return 0;
 }
 
-static int (*reloc_handlers_rela[]) (struct module *me, u32 *location,
-				Elf_Addr v) = {
-	[R_RISCV_32]			= apply_r_riscv_32_rela,
-	[R_RISCV_64]			= apply_r_riscv_64_rela,
-	[R_RISCV_BRANCH]		= apply_r_riscv_branch_rela,
-	[R_RISCV_JAL]			= apply_r_riscv_jal_rela,
-	[R_RISCV_RVC_BRANCH]		= apply_r_riscv_rvc_branch_rela,
-	[R_RISCV_RVC_JUMP]		= apply_r_riscv_rvc_jump_rela,
-	[R_RISCV_PCREL_HI20]		= apply_r_riscv_pcrel_hi20_rela,
-	[R_RISCV_PCREL_LO12_I]		= apply_r_riscv_pcrel_lo12_i_rela,
-	[R_RISCV_PCREL_LO12_S]		= apply_r_riscv_pcrel_lo12_s_rela,
-	[R_RISCV_HI20]			= apply_r_riscv_hi20_rela,
-	[R_RISCV_LO12_I]		= apply_r_riscv_lo12_i_rela,
-	[R_RISCV_LO12_S]		= apply_r_riscv_lo12_s_rela,
-	[R_RISCV_GOT_HI20]		= apply_r_riscv_got_hi20_rela,
-	[R_RISCV_CALL_PLT]		= apply_r_riscv_call_plt_rela,
-	[R_RISCV_CALL]			= apply_r_riscv_call_rela,
-	[R_RISCV_RELAX]			= apply_r_riscv_relax_rela,
-	[R_RISCV_ALIGN]			= apply_r_riscv_align_rela,
-	[R_RISCV_ADD16]			= apply_r_riscv_add16_rela,
-	[R_RISCV_ADD32]			= apply_r_riscv_add32_rela,
-	[R_RISCV_ADD64]			= apply_r_riscv_add64_rela,
-	[R_RISCV_SUB16]			= apply_r_riscv_sub16_rela,
-	[R_RISCV_SUB32]			= apply_r_riscv_sub32_rela,
-	[R_RISCV_SUB64]			= apply_r_riscv_sub64_rela,
+static int dynamic_linking_not_supported(struct module *me, void *location,
+					 Elf_Addr v)
+{
+	pr_err("%s: Dynamic linking not supported in kernel modules PC = %p\n",
+	       me->name, location);
+	return -EINVAL;
+}
+
+static int tls_not_supported(struct module *me, void *location, Elf_Addr v)
+{
+	pr_err("%s: Thread local storage not supported in kernel modules PC = %p\n",
+	       me->name, location);
+	return -EINVAL;
+}
+
+static int apply_r_riscv_sub6_rela(struct module *me, void *location, Elf_Addr v)
+{
+	u8 *byte = location;
+	u8 value = v;
+
+	*byte = (*byte - (value & 0x3f)) & 0x3f;
+	return 0;
+}
+
+static int apply_r_riscv_set6_rela(struct module *me, void *location, Elf_Addr v)
+{
+	u8 *byte = location;
+	u8 value = v;
+
+	*byte = (*byte & 0xc0) | (value & 0x3f);
+	return 0;
+}
+
+static int apply_r_riscv_set8_rela(struct module *me, void *location, Elf_Addr v)
+{
+	*(u8 *)location = (u8)v;
+	return 0;
+}
+
+static int apply_r_riscv_set16_rela(struct module *me, void *location,
+				    Elf_Addr v)
+{
+	*(u16 *)location = (u16)v;
+	return 0;
+}
+
+static int apply_r_riscv_set32_rela(struct module *me, void *location,
+				    Elf_Addr v)
+{
+	*(u32 *)location = (u32)v;
+	return 0;
+}
+
+static int apply_r_riscv_32_pcrel_rela(struct module *me, void *location,
+				       Elf_Addr v)
+{
+	*(u32 *)location = v - (uintptr_t)location;
+	return 0;
+}
+
+static int apply_r_riscv_plt32_rela(struct module *me, void *location,
+				    Elf_Addr v)
+{
+	ptrdiff_t offset = (void *)v - location;
+
+	if (!riscv_insn_valid_32bit_offset(offset)) {
+		/* Only emit the plt entry if offset over 32-bit range */
+		if (IS_ENABLED(CONFIG_MODULE_SECTIONS)) {
+			offset = (void *)module_emit_plt_entry(me, v) - location;
+		} else {
+			pr_err("%s: target %016llx can not be addressed by the 32-bit offset from PC = %p\n",
+			       me->name, (long long)v, location);
+			return -EINVAL;
+		}
+	}
+
+	*(u32 *)location = (u32)offset;
+	return 0;
+}
+
+static int apply_r_riscv_set_uleb128(struct module *me, void *location, Elf_Addr v)
+{
+	*(long *)location = v;
+	return 0;
+}
+
+static int apply_r_riscv_sub_uleb128(struct module *me, void *location, Elf_Addr v)
+{
+	*(long *)location -= v;
+	return 0;
+}
+
+static int apply_6_bit_accumulation(struct module *me, void *location, long buffer)
+{
+	u8 *byte = location;
+	u8 value = buffer;
+
+	if (buffer > 0x3f) {
+		pr_err("%s: value %ld out of range for 6-bit relocation.\n",
+		       me->name, buffer);
+		return -EINVAL;
+	}
+
+	*byte = (*byte & 0xc0) | (value & 0x3f);
+	return 0;
+}
+
+static int apply_8_bit_accumulation(struct module *me, void *location, long buffer)
+{
+	if (buffer > U8_MAX) {
+		pr_err("%s: value %ld out of range for 8-bit relocation.\n",
+		       me->name, buffer);
+		return -EINVAL;
+	}
+	*(u8 *)location = (u8)buffer;
+	return 0;
+}
+
+static int apply_16_bit_accumulation(struct module *me, void *location, long buffer)
+{
+	if (buffer > U16_MAX) {
+		pr_err("%s: value %ld out of range for 16-bit relocation.\n",
+		       me->name, buffer);
+		return -EINVAL;
+	}
+	*(u16 *)location = (u16)buffer;
+	return 0;
+}
+
+static int apply_32_bit_accumulation(struct module *me, void *location, long buffer)
+{
+	if (buffer > U32_MAX) {
+		pr_err("%s: value %ld out of range for 32-bit relocation.\n",
+		       me->name, buffer);
+		return -EINVAL;
+	}
+	*(u32 *)location = (u32)buffer;
+	return 0;
+}
+
+static int apply_64_bit_accumulation(struct module *me, void *location, long buffer)
+{
+	*(u64 *)location = (u64)buffer;
+	return 0;
+}
+
+static int apply_uleb128_accumulation(struct module *me, void *location, long buffer)
+{
+	/*
+	 * ULEB128 is a variable length encoding. Encode the buffer into
+	 * the ULEB128 data format.
+	 */
+	u8 *p = location;
+
+	while (buffer != 0) {
+		u8 value = buffer & 0x7f;
+
+		buffer >>= 7;
+		value |= (!!buffer) << 7;
+
+		*p++ = value;
+	}
+	return 0;
+}
+
+/*
+ * Relocations defined in the riscv-elf-psabi-doc.
+ * This handles static linking only.
+ */
+static const struct relocation_handlers reloc_handlers[] = {
+	[R_RISCV_32] = { apply_r_riscv_32_rela },
+	[R_RISCV_64] = { apply_r_riscv_64_rela },
+	[R_RISCV_RELATIVE] = { dynamic_linking_not_supported },
+	[R_RISCV_COPY] = { dynamic_linking_not_supported },
+	[R_RISCV_JUMP_SLOT] = { dynamic_linking_not_supported },
+	[R_RISCV_TLS_DTPMOD32] = { dynamic_linking_not_supported },
+	[R_RISCV_TLS_DTPMOD64] = { dynamic_linking_not_supported },
+	[R_RISCV_TLS_DTPREL32] = { dynamic_linking_not_supported },
+	[R_RISCV_TLS_DTPREL64] = { dynamic_linking_not_supported },
+	[R_RISCV_TLS_TPREL32] = { dynamic_linking_not_supported },
+	[R_RISCV_TLS_TPREL64] = { dynamic_linking_not_supported },
+	/* 12-15 undefined */
+	[R_RISCV_BRANCH] = { apply_r_riscv_branch_rela },
+	[R_RISCV_JAL] = { apply_r_riscv_jal_rela },
+	[R_RISCV_CALL] = { apply_r_riscv_call_rela },
+	[R_RISCV_CALL_PLT] = { apply_r_riscv_call_plt_rela },
+	[R_RISCV_GOT_HI20] = { apply_r_riscv_got_hi20_rela },
+	[R_RISCV_TLS_GOT_HI20] = { tls_not_supported },
+	[R_RISCV_TLS_GD_HI20] = { tls_not_supported },
+	[R_RISCV_PCREL_HI20] = { apply_r_riscv_pcrel_hi20_rela },
+	[R_RISCV_PCREL_LO12_I] = { apply_r_riscv_pcrel_lo12_i_rela },
+	[R_RISCV_PCREL_LO12_S] = { apply_r_riscv_pcrel_lo12_s_rela },
+	[R_RISCV_HI20] = { apply_r_riscv_hi20_rela },
+	[R_RISCV_LO12_I] = { apply_r_riscv_lo12_i_rela },
+	[R_RISCV_LO12_S] = { apply_r_riscv_lo12_s_rela },
+	[R_RISCV_TPREL_HI20] = { tls_not_supported },
+	[R_RISCV_TPREL_LO12_I] = { tls_not_supported },
+	[R_RISCV_TPREL_LO12_S] = { tls_not_supported },
+	[R_RISCV_TPREL_ADD] = { tls_not_supported },
+	[R_RISCV_ADD8] = { apply_r_riscv_add8_rela, apply_8_bit_accumulation },
+	[R_RISCV_ADD16] = { apply_r_riscv_add16_rela,
+			    apply_16_bit_accumulation },
+	[R_RISCV_ADD32] = { apply_r_riscv_add32_rela,
+			    apply_32_bit_accumulation },
+	[R_RISCV_ADD64] = { apply_r_riscv_add64_rela,
+			    apply_64_bit_accumulation },
+	[R_RISCV_SUB8] = { apply_r_riscv_sub8_rela, apply_8_bit_accumulation },
+	[R_RISCV_SUB16] = { apply_r_riscv_sub16_rela,
+			    apply_16_bit_accumulation },
+	[R_RISCV_SUB32] = { apply_r_riscv_sub32_rela,
+			    apply_32_bit_accumulation },
+	[R_RISCV_SUB64] = { apply_r_riscv_sub64_rela,
+			    apply_64_bit_accumulation },
+	/* 41-42 reserved for future standard use */
+	[R_RISCV_ALIGN] = { apply_r_riscv_align_rela },
+	[R_RISCV_RVC_BRANCH] = { apply_r_riscv_rvc_branch_rela },
+	[R_RISCV_RVC_JUMP] = { apply_r_riscv_rvc_jump_rela },
+	/* 46-50 reserved for future standard use */
+	[R_RISCV_RELAX] = { apply_r_riscv_relax_rela },
+	[R_RISCV_SUB6] = { apply_r_riscv_sub6_rela, apply_6_bit_accumulation },
+	[R_RISCV_SET6] = { apply_r_riscv_set6_rela, apply_6_bit_accumulation },
+	[R_RISCV_SET8] = { apply_r_riscv_set8_rela, apply_8_bit_accumulation },
+	[R_RISCV_SET16] = { apply_r_riscv_set16_rela,
+			    apply_16_bit_accumulation },
+	[R_RISCV_SET32] = { apply_r_riscv_set32_rela,
+			    apply_32_bit_accumulation },
+	[R_RISCV_32_PCREL] = { apply_r_riscv_32_pcrel_rela },
+	[R_RISCV_IRELATIVE] = { dynamic_linking_not_supported },
+	[R_RISCV_PLT32] = { apply_r_riscv_plt32_rela },
+	[R_RISCV_SET_ULEB128] = { apply_r_riscv_set_uleb128,
+				  apply_uleb128_accumulation },
+	[R_RISCV_SUB_ULEB128] = { apply_r_riscv_sub_uleb128,
+				  apply_uleb128_accumulation },
+	/* 62-191 reserved for future standard use */
+	/* 192-255 nonstandard ABI extensions  */
 };
 
+void process_accumulated_relocations(struct module *me)
+{
+	/*
+	 * Only ADD/SUB/SET/ULEB128 should end up here.
+	 *
+	 * Each bucket may have more than one relocation location. All
+	 * relocations for a location are stored in a list in a bucket.
+	 *
+	 * Relocations are applied to a temp variable before being stored to the
+	 * provided location to check for overflow. This also allows ULEB128 to
+	 * properly decide how many entries are needed before storing to
+	 * location. The final value is stored into location using the handler
+	 * for the last relocation to an address.
+	 *
+	 * Three layers of indexing:
+	 *	- Each of the buckets in use
+	 *	- Groups of relocations in each bucket by location address
+	 *	- Each relocation entry for a location address
+	 */
+	struct used_bucket *bucket_iter;
+	struct relocation_head *rel_head_iter;
+	struct relocation_entry *rel_entry_iter;
+	int curr_type;
+	void *location;
+	long buffer;
+
+	list_for_each_entry(bucket_iter, &used_buckets_list, head) {
+		hlist_for_each_entry(rel_head_iter, bucket_iter->bucket, node) {
+			buffer = 0;
+			location = rel_head_iter->location;
+			list_for_each_entry(rel_entry_iter,
+					    rel_head_iter->rel_entry, head) {
+				curr_type = rel_entry_iter->type;
+				reloc_handlers[curr_type].reloc_handler(
+					me, &buffer, rel_entry_iter->value);
+				kfree(rel_entry_iter);
+			}
+			reloc_handlers[curr_type].accumulate_handler(
+				me, location, buffer);
+			kfree(rel_head_iter);
+		}
+		kfree(bucket_iter);
+	}
+
+	kfree(relocation_hashtable);
+}
+
+int add_relocation_to_accumulate(struct module *me, int type, void *location,
+				 unsigned int hashtable_bits, Elf_Addr v)
+{
+	struct relocation_entry *entry;
+	struct relocation_head *rel_head;
+	struct hlist_head *current_head;
+	struct used_bucket *bucket;
+	unsigned long hash;
+
+	entry = kmalloc(sizeof(*entry), GFP_KERNEL);
+	INIT_LIST_HEAD(&entry->head);
+	entry->type = type;
+	entry->value = v;
+
+	hash = hash_min((uintptr_t)location, hashtable_bits);
+
+	current_head = &relocation_hashtable[hash];
+
+	/* Find matching location (if any) */
+	bool found = false;
+	struct relocation_head *rel_head_iter;
+
+	hlist_for_each_entry(rel_head_iter, current_head, node) {
+		if (rel_head_iter->location == location) {
+			found = true;
+			rel_head = rel_head_iter;
+			break;
+		}
+	}
+
+	if (!found) {
+		rel_head = kmalloc(sizeof(*rel_head), GFP_KERNEL);
+		rel_head->rel_entry =
+			kmalloc(sizeof(struct list_head), GFP_KERNEL);
+		INIT_LIST_HEAD(rel_head->rel_entry);
+		rel_head->location = location;
+		INIT_HLIST_NODE(&rel_head->node);
+		if (!current_head->first) {
+			bucket =
+				kmalloc(sizeof(struct used_bucket), GFP_KERNEL);
+			INIT_LIST_HEAD(&bucket->head);
+			bucket->bucket = current_head;
+			list_add(&bucket->head, &used_buckets_list);
+		}
+		hlist_add_head(&rel_head->node, current_head);
+	}
+
+	/* Add relocation to head of discovered rel_head */
+	list_add_tail(&entry->head, rel_head->rel_entry);
+
+	return 0;
+}
+
+unsigned int initialize_relocation_hashtable(unsigned int num_relocations)
+{
+	/* Can safely assume that bits is not greater than sizeof(long) */
+	unsigned long hashtable_size = roundup_pow_of_two(num_relocations);
+	unsigned int hashtable_bits = ilog2(hashtable_size);
+
+	/*
+	 * Double size of hashtable if num_relocations * 1.25 is greater than
+	 * hashtable_size.
+	 */
+	int should_double_size = ((num_relocations + (num_relocations >> 2)) > (hashtable_size));
+
+	hashtable_bits += should_double_size;
+
+	hashtable_size <<= should_double_size;
+
+	relocation_hashtable = kmalloc_array(hashtable_size,
+					     sizeof(*relocation_hashtable),
+					     GFP_KERNEL);
+	__hash_init(relocation_hashtable, hashtable_size);
+
+	INIT_LIST_HEAD(&used_buckets_list);
+
+	return hashtable_bits;
+}
+
 int apply_relocate_add(Elf_Shdr *sechdrs, const char *strtab,
 		       unsigned int symindex, unsigned int relsec,
 		       struct module *me)
 {
 	Elf_Rela *rel = (void *) sechdrs[relsec].sh_addr;
-	int (*handler)(struct module *me, u32 *location, Elf_Addr v);
+	int (*handler)(struct module *me, void *location, Elf_Addr v);
 	Elf_Sym *sym;
-	u32 *location;
+	void *location;
 	unsigned int i, type;
 	Elf_Addr v;
 	int res;
+	unsigned int num_relocations = sechdrs[relsec].sh_size / sizeof(*rel);
+	unsigned int hashtable_bits = initialize_relocation_hashtable(num_relocations);
 
 	pr_debug("Applying relocate section %u to %u\n", relsec,
 	       sechdrs[relsec].sh_info);
 
-	for (i = 0; i < sechdrs[relsec].sh_size / sizeof(*rel); i++) {
+	for (i = 0; i < num_relocations; i++) {
 		/* This is where to make the change */
 		location = (void *)sechdrs[sechdrs[relsec].sh_info].sh_addr
 			+ rel[i].r_offset;
@@ -370,8 +760,8 @@ int apply_relocate_add(Elf_Shdr *sechdrs, const char *strtab,
 
 		type = ELF_RISCV_R_TYPE(rel[i].r_info);
 
-		if (type < ARRAY_SIZE(reloc_handlers_rela))
-			handler = reloc_handlers_rela[type];
+		if (type < ARRAY_SIZE(reloc_handlers))
+			handler = reloc_handlers[type].reloc_handler;
 		else
 			handler = NULL;
 
@@ -427,11 +817,16 @@ int apply_relocate_add(Elf_Shdr *sechdrs, const char *strtab,
 			}
 		}
 
-		res = handler(me, location, v);
+		if (reloc_handlers[type].accumulate_handler)
+			res = add_relocation_to_accumulate(me, type, location, hashtable_bits, v);
+		else
+			res = handler(me, location, v);
 		if (res)
 			return res;
 	}
 
+	process_accumulated_relocations(me);
+
 	return 0;
 }